1. Field of the Invention
The invention relates to an image forming apparatus.
2. Description of Related Art
Since print density (thickness) using toner serving as developer may vary from thick to thin due to environmental or temporal changes, a conventional image forming apparatus such as an electrophotographic printer or a copier detects the density of printing with a densitometer and executes a density correction in order to maintain the print density constant. For example, Japanese Patent Application Laid-Open No. 2004-341100 discloses a technique capable of high-quality printing by compensating for the sensitivity of a densitometer.
In a conventional image forming apparatus, when the toner take-out is continuously low, most of the toner spends more time on the developing roller and thus may become triboelectrifically charged to an excessive level. When such excessively charged toner is transferred to an electrostatic latent image on the photosensitive drum, the excessively charged toner is attached to the photosensitive drum more than necessary. This causes excessively high density portions, that is, smears on the printed paper sheet.